JP2001103657A - Method of detecting tracking short circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method by which the occurrence of an electric current caused by a tracking short circuit can be detected accurately without making errors in detection, even when the rush current of a household electric appliance or a load current becomes larger due to an increased number of used household electric appliances. SOLUTION: In a method for detecting tracking short circuit, an electrical current flowing into an electric path is detected and the frequency distribution of the variation of a current value detected within a prescribed period of time is measured. When the ratio of the frequency in a prescribed variation section of the measured frequency distribution of the current variation to the frequency in the whole section of the distribution meets a set criterion, occurrence of tracking is detected by outputting a detection signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a tracking short circuit in an electric circuit.

[0002]

2. Description of the Related Art Conventionally, as a method of detecting a short circuit occurring in an electric circuit, a current value is detected by using a current transformer by combining an electronic circuit, and the current value is converted into a voltage value by a current-voltage conversion circuit. There is known a configuration in which the occurrence of a short circuit is detected based on an A / D conversion value converted by an A / D conversion circuit. In such a short-circuit detecting device, the A / D converted value after the A / D conversion is integrated by the integrating circuit for a predetermined time, and when the integrated value exceeds a predetermined reference value, a short-circuit detecting signal is output. Is configured to be detected.

As a method for detecting a tracking short circuit, in a current value detected for each detection unit time in a certain range, for example, the second detection value is smaller than the first detection value and is smaller than the second detection value by three. There is known a method of detecting a tracking short circuit based on a method of changing the absolute value of the current value, such as detecting when the second detection value is large.

[0004]

Since the short circuit detection according to the prior art is performed by integrating current values for a predetermined time, a short circuit current having a relatively low value such as a tracking short circuit is detected. Requires that the predetermined reference value be kept small. In this case, erroneous detection may be caused, for example, when the inrush current of the home electric appliance or the load current increases when a plurality of home electric appliances are used.

When a plurality of home appliances are used at the same time, the detected current value may change in a manner similar to that of tracking, and it may be difficult to accurately detect the occurrence of a tracking short-circuit current. Was.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and a detection method capable of accurately detecting the occurrence of a tracking short-circuit current without erroneously detecting an inrush current of a home appliance or a current caused by a plurality of home appliances. The challenge is to obtain

[0007]

Means for Solving the Problems The present invention takes the following means in order to solve such problems. That is, in claim 1, the tracking short detection method according to the present invention detects a current flowing in an electric circuit, measures a frequency distribution of an absolute value of a variation amount of the current value within the predetermined time, and calculates a variation of the current value. In the frequency distribution of the quantity, when the frequency of the predetermined fluctuation amount section is equal to or more than the determination reference with respect to the frequency of the entire distribution section, it is determined that the tracking short circuit has occurred.

According to a second aspect of the present invention, a current flowing through the electric circuit is detected, and a current value in absolute value used for determination of tracking short circuit is extracted from a current waveform obtained for each unit time obtained by dividing a predetermined time into a plurality of times. A tracking short circuit occurred when the difference between adjacent current values among the current values extracted per unit time was taken as the fluctuation amount per unit time, and when the frequency of a predetermined fluctuation amount section satisfied the set criterion, the tracking short circuit occurred. It is determined that a tracking short circuit has occurred.

According to a third aspect of the present invention, it is determined whether or not the frequency of the predetermined variation amount section satisfies a set determination criterion with respect to the determination criterion set for each of the plurality of predetermined variation amount sections. This is performed so that it is determined that a tracking short circuit has occurred when all the criteria are satisfied.

According to a fourth aspect of the present invention, an absolute current value used for determining a tracking short circuit is extracted from a current waveform obtained for each unit time obtained by dividing a predetermined time into a plurality of unit times, and extracted for each adjacent unit time. The difference between the obtained current values is taken as the fluctuation amount per unit time, and the data of the oldest fluctuation amount in the time series is excluded each time the unit time elapses, and at the same time, it is calculated from the current value extracted at the new unit time The data of the fluctuation amount is added, and the occurrence of the tracking short circuit is determined based on the fluctuation amount of the current value within a predetermined time which is constantly updated in unit time.

According to a fifth aspect of the present invention, in the tracking short-circuit detection processing within the predetermined time, the unit time obtained by dividing the predetermined time into a plurality of times is further divided into times, and the absolute value of the current peak value within the divided time is converted. Is extracted, and the difference between the current peak values is calculated for each adjacent divided time period, and is used as a variation. When there is, the tracking short detection process is initialized and the process is newly started.

[0012]

In the above means, the frequency distribution of the current fluctuation within a predetermined time is measured, so that the frequency of the current fluctuation in each section of the frequency distribution can be grasped, and the fluctuation of the current value can be obtained. Of the frequency distribution of the quantity,
The distribution of the frequency of the predetermined fluctuation section is monitored by the ratio of the frequency to the frequency of the entire section, so that the difference in the current fluctuation caused by tracking short circuit and the use of home appliances can be distinguished, and the set value of the judgment criterion and the predetermined fluctuation section can be appropriately determined. With this setting, occurrence of tracking short circuit can be determined without malfunction.

According to a second aspect of the present invention, an absolute value of a current value used for determining a tracking short circuit is extracted from a current waveform obtained for each unit time obtained by dividing a predetermined time for detecting a current flowing through an electric circuit into a plurality of unit times. The difference between adjacent current values among the current values extracted for each time is taken as a variation per unit time, and a predetermined variation is determined in order to determine whether or not the frequency of the predetermined variation section satisfies the set criterion. It is possible to determine that a tracking short circuit has occurred only in the frequency of the volume section, simplify the determination process, and determine the unit time, the predetermined fluctuation section, and the determination criterion appropriately, so that the load current waveform of the home appliance and the tracking short circuit Can be correctly distinguished.

According to the present invention, the occurrence of the tracking short circuit can be detected more accurately by providing a plurality of conditions as to whether or not the frequency of the predetermined fluctuation amount section satisfies a predetermined judgment criterion.

According to a fourth aspect of the present invention, the absolute value of the current value used for the determination of the tracking short circuit is extracted from the current waveform obtained for each unit time obtained by dividing the predetermined time into a plurality of times, and extracted for each unit time. Of the current values, the difference between adjacent current values was taken as the fluctuation amount per unit time, and the oldest fluctuation data in the time series was excluded every time the unit time passed, and extracted at the new unit time Since the current fluctuation amount is newly added and the determination is performed based on the fluctuation amount of the current value within a predetermined time constantly updated by the unit time, the latest current waveform can be constantly monitored,
The memory of the microcomputer used for the circuit can be minimized.

According to a fifth aspect of the present invention, in the tracking short detection processing within the predetermined time, the unit time obtained by dividing the predetermined time into a plurality of times is further divided into time, and the absolute value of the current peak value within the divided time is obtained. Is extracted, and the difference between the current peak values is taken for each adjacent divided time, and the difference is taken as the amount of variation,
The tracking short-circuit detection processing is continued when the fluctuation amount is individually equal to or more than a predetermined amount, and when there is a fluctuation amount equal to or less than the predetermined amount, the tracking short-circuit detection processing is initialized and a new processing is started. Unless the tracking short-circuit determination process is continued for all of the unit times within the period, the tracking short-circuit is not finally determined, and erroneous detection can be prevented.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a tracking short-circuit detecting method characterized by detecting a current flowing through an electric circuit and detecting occurrence of tracking based on a variation of a current value detected within a predetermined time. .

An embodiment in which the detection method according to the present invention is applied to a circuit breaker will be described below with reference to the drawings.

FIG. 1 is a block diagram of a circuit of an embodiment of a circuit breaker using the detection method according to claim 1 of the present invention. As shown in FIG. 1, a circuit using the tracking short detection method of the present embodiment includes a current transformer 1 and a current-voltage conversion circuit 2.
, A rectifier circuit 3 and a determination circuit 11.

The current transformer 1 detects an electric current flowing through the electric circuit 10 and outputs an alternating current.

The current-voltage conversion circuit 2 converts the AC current output from the current transformer 1 into an AC voltage, and specifically converts the voltage into a voltage value through a resistor.

The rectifier circuit 3 rectifies the output voltage of the current-to-voltage converter circuit 2 using a diode or the like. When digitizing, the resolution of the A / D conversion value can be increased, and the current value is converted to an absolute value.

The determination circuit 11 constantly monitors the voltage value output from the rectifier circuit 3 to determine whether the monitored current corresponds to a tracking short circuit. If the tracking current is determined to be a tracking short circuit, the trip circuit shuts off the circuit. Output an instruction signal,
A trip coil is configured to trip the circuit breaker contact.

The decision circuit 11 includes an A / D conversion circuit 4, a central processing circuit 12, a register circuit 13, and a decision output circuit 6.
It is comprised including.

The A / D conversion circuit 4 converts the output voltage of the rectification circuit 3 to a predetermined time width (sampling time) of several milliseconds or less.
And converts the magnitude of the voltage into an A / D conversion value of a digital signal. The sampling time is, for example, about 0.25 millisecond.

As an example, assuming that the maximum input voltage of the A / D conversion circuit 4 is 5 V and the resolution of digital conversion is 8 bits, the relationship between the voltage input to the A / D conversion circuit 4 and the output is 0 V Is 0, 2.5V is 127, and 5V is 255. Here, the current-voltage conversion circuit 2 is set so that the 1-bit current value at the time of A / D conversion corresponds to 1A.
Is adjusted, the performance of the A / D conversion circuit 4 becomes 0 A to
Current waveforms up to +255 A can be measured. Also,
As a means for converting into a digital signal, a central processing circuit 12 incorporating the A / D conversion circuit 4 may be used.

The central processing circuit 12 performs a numerical operation on the amount of current fluctuation based on the A / D converted value obtained by the A / D conversion circuit 4 and outputs current fluctuation amount data to the register circuit 13. Further, the variation amount data stored in the register circuit 13 is read, and tracking short-circuit determination is performed by a built-in program. When it is determined that tracking short-circuit occurs, a determination signal is output to the determination output circuit 6.

The register circuit 13 excludes the oldest current fluctuation value each time a new current fluctuation value is output from the central processing circuit 12, and reads and stores the newest current fluctuation value. Therefore, a plurality of current fluctuation values within a predetermined time are always stored in chronological order. Further, in order to improve the determination accuracy, it is preferable to provide seven or more always new values of the current fluctuation amount to be stored. It is preferable to be able to store the possible number according to the memory capacity inside the microcomputer and according to the length of the determination time.

The judgment output circuit 6 receives the judgment signal output from the central processing circuit 12, and outputs a signal to the trip circuit.

The method of determining the tracking short-circuit by the central processing circuit 12 is performed as follows in the case of the method according to the first aspect.

The central processing circuit 12 extracts the peak current value for each half-wave from the data for each sampling time sent from the A / D conversion circuit 4 and compares it with the peak current value of the immediately preceding half-wave. , The difference as the current variation, the register circuit 13
To send to. The register circuit 13 stores the current fluctuation amount for a predetermined time as data, and when new data is received from the central processing circuit 12, the oldest data is discarded.
Import the latest data. The predetermined time is 0.2
On the order of seconds.

The central processing circuit 12 sends out the latest data to the register circuit 13 and, at the same time, fetches the current fluctuation amount data for a predetermined time from the register circuit 13 and obtains the current fluctuation amount from the frequency corresponding to the fluctuation amount of each data. , The frequency distribution of the variation as shown in FIG. 2 is calculated, and from this frequency distribution, the frequency of the predetermined variation amount section appropriately determined and the frequency of the entire distribution section are calculated. The ratio of the frequency in the predetermined fluctuation amount section is calculated, and it is determined whether or not the ratio is equal to or greater than a determination reference.

FIG. 6 shows an example of the frequency distribution of the variation of the current corresponding to FIG. 2 in the case where the current is due to the use of home electric appliances. You can see that it is doing. On the other hand, FIG. 2 is an example of the frequency distribution of the amount of current fluctuation in the case of tracking short-circuit,
It can be seen that many frequencies appear in the section where the variation amount is 5 to 30A. Therefore, it is calculated from the frequency distribution of the current fluctuation amount within a predetermined time, how many percent of the frequency of the fluctuation amount section of 5 to 30 A corresponds to the frequency of the entire distribution section, and whether the frequency is equal to or greater than a predetermined determination reference value. If you decide whether
Even if the magnitude of the current flowing is almost the same for home appliances and tracking short-circuits and it is indistinguishable, it is possible to accurately determine whether the current is due to the use of home appliances or due to tracking short-circuit from the current fluctuation amount it can.

In the case of the method according to the second aspect, the tracking short circuit determination method of the central processing circuit 12 is performed as follows. The determination of the central processing circuit 12 is performed based on data within a predetermined time. The predetermined time is about 0.2 seconds in this example.

FIG. 3 shows a predetermined time and a unit time A (i), an extraction current IPA (i) per unit time, and a current variation delta IP.
It is a conceptual diagram of A (i). The predetermined time is a unit time A (i)
(I = 1 to n) (n is a positive integer).
The IPA (i) receives data transmission from the A / D conversion circuit 4 of FIG.
Is the current value extracted within the unit time A (i). In this example, the peak current value is within the unit time A (i).
The average value within the unit time A (i) may be used. Delta IPA (i) is one of the current values extracted per unit time.
IPA is the variation calculated by taking the difference between adjacent current values.
It is represented by the difference between (i) and IPA (i-1).

In the conceptual diagram of FIG. 3, the register circuit 13 includes n of delta IPA (1) to delta IPA (n).
And IPA (n) data. Initially, the stored individual data values are zero.

Next, the central processing circuit 12, which has received data from the A / D conversion circuit 4 at every sampling time, extracts the peak current value IPA (n + 1) within the unit time A (n + 1) and simultaneously registers the peak current value IPA (n + 1). 13 to receive the previous extracted current value (peak current value) IPA (n), calculate Delta IPA (n + 1) = IPA (n + 1) -IPA (n), and newly add Delta IPA (n + 1) to the register circuit 13. However, when the delta IPA (n + 1) becomes negative, it is replaced with a positive value and transmitted.

The delta IPA (n +
1) Before transmission, the register circuit 13 stores the current variation delta IPA per unit time A (i) as shown in FIG.
Although (1) to n pieces of data of delta IPA (n) are stored, when data transmission of a new current variation delta IPA (n + 1) is received from the central processing circuit 12, the oldest data delta IPA is received. (1) is discarded and at the same time delta IPA (2) is replaced with delta IPA (1), delta IPA
(3) is converted to delta IPA (2)... Delta IPA (n +
1) is stored again as delta IPA (n). At the same time, the central processing circuit 12 receives the updated data delta IPA (1) to delta IPA (n) of the current variation amount from the register circuit 13 and sets the delta IPA (i) to 5
The number of data that is not less than A and less than 30A is summed up as a frequency, and when the frequency is n × 0.7 or more, a determination signal indicating tracking short circuit is sent to the determination output circuit.

According to the tracking short detection method described above, in the method according to the first aspect, the central processing circuit 12 creates the frequency distribution table and calculates the ratio. Whether or not a tracking short circuit has occurred can be determined by a simple determination process using only the total value of the number of data in a predetermined section.

According to the third aspect, in addition to the determination that the current variation is in the section of 5 to 30 A, the frequency of the current variation in the section of 11 A to 30 A is n × 0.4 or more. Whether or not a tracking short circuit has occurred is determined when both conditions are satisfied. By doing so, it is possible to further improve the determination accuracy of the current due to the use of the home electric appliance and the current due to the tracking short circuit.

FIG. 5 is a conceptual diagram for explaining a fifth embodiment of the present invention. The unit time A (i) is m (m
Is a positive integer) and is divided into time periods of Ta (i, 1) to Ta (i, m). In the present embodiment, Ta (i, j) is substantially the time of a half-wave of the frequency of the commercial AC power. Since the period differs between 50 Hz and 60 Hz depending on the area, the interval is set to about 9 ms.

In FIG. 5, IPT (i, j) is a peak current value at a divided time Ta (i, j), and delta IPT (i, j) = IPT (i, j) -IPT (i, j).
-1). The central processing circuit 12, which has received data from the A / D conversion circuit 4 at each sampling time, extracts the peak current value IPT (i, j) within the divided time, and extracts the previous IPT (i, j). i, j-1) data, delta IPT (i, j) = IPT (i, j) -IPT
(I, j-1) is calculated. If the delta IPT (i, j) becomes negative, it is replaced with a positive value.

The central processing circuit 12 has the above-mentioned unit time A
In parallel with the extraction of the peak current value delta IPA (i) for each (i), for the time Ta (i, 1) to Ta (i, m) obtained by dividing the unit time A (i) into m pieces, Calculate the above delta IPT (i, j) and calculate the calculated delta IPT
If (i, j) is equal to or more than a certain value (5A is set in this embodiment), the next delta-delta IPT (i, j)
In the calculation of j), when the next delta IPT (i, j) is less than a certain value, the processing of the preceding claims 2 and 3 is performed.
It works to initialize all the processing and to repeat the judgment processing again.

That is, the delta I within the unit time A (i)
If PT (i, 2) to delta IPT (i, m) are all equal to or more than a certain value, the process is continued, and the peak current value delta IPA (i) within the unit time A (i) is extracted. The difference from the adjacent peak current value IPA (i-1) is obtained and extracted as the current variation delta IPA (i) in the register circuit 13. If not, the data in the register circuit 13 is also initialized. Therefore, in order for the central processing circuit 12 to finally output the determination that the flowing current is a tracking short circuit to the determination output circuit of FIG. 1, the unit times A (1) to A (n) within a predetermined time are used. ), The delta IPT (i, 2) to delta IPT (i, 2,
A condition that m) is equal to or more than a certain value and processing is continued, and the amount of current fluctuation for each unit time A (i) to A (n) is a condition according to claim 2 or 3. Needs to be satisfied. In a tracking short circuit, the delta IPT (i, j) often continues for a certain amount or more, and in the invention according to claim 5, it is possible to accurately determine whether the current flowing through the circuit is due to the tracking short circuit. As a result, malfunctions are eliminated.

Although the description of the embodiment has been made with reference to the case where the present invention is applied to a circuit breaker, the present invention can also be applied to a type that issues an alarm based on the output of the judgment circuit 11 and an outlet as an object to be incorporated. It is not limited to a circuit breaker.

[0046]

As described above, according to the present invention, the detection of the tracking short circuit is performed based on the amount of change in the current. Even if the current is less than the operating current, it is possible to determine the tracking short circuit in a short time, and it will not malfunction due to the load current or inrush current of home appliances, and even if multiple home appliances are used at the same time, tracking If a short circuit occurs in parallel,
By detecting the characteristic amount of current fluctuation generated by the tracking short circuit, it is possible to reliably determine the tracking short circuit and to obtain a detection method with less malfunction.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating a first embodiment of the present invention;

FIG. 2 is a graph showing an example of a frequency distribution of a variation amount of a tracking short-circuit current.

FIG. 3 is a conceptual diagram showing a detection method according to a second embodiment of the present invention.

FIG. 4 shows a register circuit 13 according to a fourth embodiment of the present invention.
Conceptual diagram showing data movement inside

FIG. 5 is a conceptual diagram showing a detection method according to a fifth embodiment of the present invention.

FIG. 6 is a graph showing an example of a frequency distribution of a variation amount of a load current of a home appliance.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Current transformer 2 Current-voltage conversion circuit 3 Rectifier circuit 4 A / D conversion circuit 6 Cutoff signal output circuit 10 Electric circuit 11 Judgment circuit 12 Central processing circuit 13 Register circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G014 AA03 AB09 AB33 AC18 5G004 AA01 AB01 BA03 CA04 DA01 DB01 DC05 DC14

Claims (5)

[Claims] 1. A tracking short-circuit detection method for detecting a current flowing in an electric circuit and detecting occurrence of a tracking short-circuit from a current value detected within a predetermined time, wherein the absolute value of a fluctuation amount of the current value within the predetermined time is determined. Measure the frequency distribution of the values,
In the frequency distribution of the fluctuation amount, it is determined that a tracking short circuit has occurred when the frequency of a predetermined fluctuation amount section is equal to or greater than a determination criterion with respect to the frequency of the entire distribution section. Detection method. 2. A tracking short-circuit detecting method for detecting a current flowing in an electric circuit and detecting occurrence of a tracking short-circuit from a current value detected within a predetermined time, wherein the tracking short-circuit is divided into a plurality of unit times. The current value obtained as an absolute value used for the determination of tracking short circuit is extracted from the obtained current waveform, and the difference between adjacent current values among the current values extracted per unit time is taken as a variation amount per unit time, and A tracking short circuit detection method characterized in that it is determined that a tracking short circuit has occurred when the frequency of the fluctuation amount section satisfies a set determination criterion. 3. A determination as to whether or not the frequency of the predetermined variation amount section satisfies a predetermined determination criterion is performed with respect to the determination criterion set for each of a plurality of predetermined variation amount sections. 3. The tracking short detection method according to claim 2, wherein it is determined that a tracking short circuit has occurred when a determination criterion is satisfied. 4. An absolute value of a current value used for tracking short-circuit determination is extracted from a current waveform obtained for each unit time obtained by dividing a predetermined time into a plurality of unit times. The difference is taken as the amount of change per unit time,
Each time the unit time elapses, the oldest fluctuation data in the time series is excluded, and the fluctuation data calculated from the current value extracted in the new unit time is added.
4. The tracking short detection method according to claim 2, wherein the occurrence of the tracking short is determined based on the amount of change in the current value within a predetermined time that is constantly updated in unit time. 5. The tracking short-circuit detection processing within the predetermined time, wherein the unit time obtained by dividing the predetermined time into a plurality of times is further time-divided, and an absolute value of the current peak value within the divided time is extracted. For each adjacent divided time, the difference between the current peak values is taken as a variation, and when the variation is individually a certain amount or more, the tracking short circuit detection processing is continued,
5. The tracking short circuit according to claim 2, wherein a tracking short circuit detection process is initialized when a variation amount equal to or less than a certain amount is detected, and a new process is started to determine occurrence of a tracking short circuit. Detection method.